<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>检查用户名</title>
    <script type="text/javascript" src="/js/jquery-3.2.1.js"></script>
    <script type="text/javascript" src="/js/ajaxByJquery/checkUsername.js"></script>
</head>
<body>

    用户名:<input type="text" id="username">
    <span id="msg"></span>
</body>
</html>